Evolution of thermal groundwater resources under the conditions of exploitation:A preliminary analysis.

Thermal groundwater may fall into the burial type (or basin type) and outcrop type (or hot spring type) according to its occurrence. The burial type occurs in the deep interiors of sedimentary basins. It has a large heat reservoir and large stored heat resources but its recharged heat resources are very limited or deficient. Exploitation of thermal groundwater of basin type may result in a continual decline in water levels of a geothermal water system owing to the depletion of the stored heat resources. Thermal groundwater of outcrop type is mostly found in mountainous areas and emerges in the form of hot springs. Both the storage and recharge resources of this type are limited. Exploitation of geothermal water in the vicinity of a hot spring may lead to a decrease in the discharge of the hot spring or even its drying-up. The water level and temperature of the geothermal water system may also fall continually. Under particular conditions, a flowing well located near a hot spring may increase thermal groundwater resources. The self-sealing function of a hot spring may cause a reduction in the discharge of the spring.